In December, a team of MIT neuroscientists published a remarkable study in which levels of harmful amyloid beta proteins were cut in half by exposing mice with early-stage Alzheimer's to flashing LED lights. No drugs, no surgery - just light.

For half a century, scientists have known that exposure to certain wavelengths of light can stimulate cellular function. In 1967, the Hungarian researcher Endre Mester attempted to treat cancerous tumors in rats with a low-power ruby laser. The cancer was unaffected, but the rats treated with the light waves experienced accelerated hair growth and wound healing.

Today, LEDs have replaced lasers, but researchers continue to investigate the curious health benefits of shining light on the body through a treatment method known as "photobiomodulation," or PBM.

PBM is slightly different than the technique used in the MIT study, in which researchers shined pulsed blue light into the eyes of mice in an attempt to reboot the brain's "gamma oscillation," the electrochemical frequency by which healthy neurons communicate.

With PBM, researchers use special headsets equipped with LEDs to shine pulsed red and near-infrared light on the outside of a patient's head and up through their nose. As with the MIT results, preliminary data suggest that photons of light passing through the skull trigger a biochemical chain reaction in the brain that can potentially reverse the degenerative effects of Alzheimer's as well as treat a range of other brain maladies.

Michael Hamblin is a professor of dermatology at the Harvard Medical School and a principal investigator at the Wellman Center for Photomedicine at Massachusetts General Hospital. He co-authored a recent study in which dementia patients with serious cognitive deficits experienced swift improvement after just 12 weeks with the VieLight Neuro, an LED headset that shines pulsed near-infrared light on five targeted areas of the brain.

"These are people who haven't been able to speak in connected sentences for weeks or months who suddenly start having a conversation, speaking in full sentences, understanding and replying," Hamblin told Seeker. "People who had to be fed by caregivers can suddenly pick up a knife and fork and start eating their own meals. Remarkable changes."

Equally remarkable were the changes that occurred after the light treatments were stopped. The cognitive and behavioral benefits reversed almost immediately. The study called for a four-week period in which light treatments were suspended, but one patient's symptoms returned with such force that his family begged for the device back.

Scientists like Hamblin believe that PBM works by stimulating the mitochondria within cells to produce more ATP, the energy that powers cellular activity.

"The mechanisms are manifold," Hamblin explained. "Clearly you're boosting metabolism - ATP, oxygen consumption, brain energy. You're improving cerebral blood flow. But you're also stimulating the formation of new brain cells and the formation of new connections between existing brain cells. And together, these two processes comprise neuroplasticity, basically the brain's ability to reorganize itself, to repair itself."

Margaret Naeser, a research professor of neurology at the Boston University School of Medicine, studies the use of PBM headsets and helmets to treat patients with traumatic brain injuries, stroke, and military veterans suffering from Gulf War Syndrome - an unexplained illness seen among those who fought in the 1991 Gulf War that can involve dizziness, insomnia, fatigue, and headaches, among other symptoms.

Naeser is in the middle of a $2.8 million study for the U.S. Department of Veterans Affairs to improve cognition and memory in vets using LED treatments. She explained that red light at 600 nm wavelengths and near-infrared light at 810 nm or 830 nm is absorbed by an enzyme inside cellular mitochondria called cytochrome c oxidase (CCO). In patients with brain injuries or disorders, the receptors on the CCO enzymes become clogged with nitric oxide.

"When you deliver near-infrared photons to that brain cell, the nitric oxide is pushed outside the cell wall, and that promotes increased blood flow, which is what you want in an area that's damaged," said Naeser. "And that's what we see on our MRI images, the increase in blood flow targeted to where we put the photons. I couldn't believe it. I was shocked."

In addition to priming blood flow in the brain, light treatments seem to boost the brain's autoimmune response to amyloid beta, the proteins that form the crippling plaque deposits found in Alzheimer's. In a healthy brain, immune cells called microglia are tasked with clearing out excess amyloid beta. In an Alzheimer's brain, microglia undergo a dangerous transformation. They not only stop attacking amyloid beta, but secrete a toxin that damages healthy brain cells.

In the MIT study, repeated exposure to blue light pulsing at the gamma frequency (40 Hz) appeared to train the Alzheimer's brain to return to its normal rhythm. In turn, it caused the microglia to return to their healthy state and start clearing out amyloid beta debris.

Naeser explained that PBM light treatments use a different pathway to fight amyloid beta - sleep.

"You and I are building up amyloid beta all day," said Naeser. "When you go to sleep at night, the cerebrospinal fluid comes in and massages the cells in the brain to pull out amyloid beta buildup, get it into the blood vessels and wash it away."

So far only a handful of small studies have put PBM to the test in treating Alzheimer's, stroke, PTSD, depression, and other brain-related disorders. The preliminary results are very promising, but Lew Lim, the founder and CEO of VieLight, said that larger and more rigorous clinical trials are needed before the FDA will approve such devices for medical use.

"Right now the VieLight Neuro is considered a general wellness device," said Lew. "For us to make a claim for Alzheimer's disease, we have to do big clinical trials. If we don't do that, the mainstream medical community is going to say it's another snake oil remedy."

Naeser, who has spent decades researching non-invasive medical treatments, including acupuncture and transcranial magnetic stimulation, said that the only way to legitimize PBM is by conducting double-blind studies that control for the placebo effect, which her current V.A. study does. Vets who sign up for the study will receive both real and "sham" treatments, and nobody - including the researchers - will know which was real or fake until the trial is complete and the data are analyzed Credibility and acceptance are likely to be the biggest obstacles facing widespread adoption of PBM. Ironically, the almost shocking simplicity and non-invasiveness of the treatments - shining light on the head for 20 minutes at a time - could be its undoing.

"In North America, if you're not a drug, you're probably not credible," said Lim. "One of the reasons that there are no big companies involved with PBM is because a lot of it is not patentable. We're one of the few with patents on this technology."

Hamblin from the Harvard Medical School said that he could see the day when every household will own at least one PBM device. He already owns several himself to help with memory, eyesight, and even hair growth. In the short term, though, there will be challenges to funding the types of studies required for PBM to compete with conventional drug therapies.

"Poor old light therapy is like a tiny grain of sand compared to the huge boulder of big pharma," said Hamblin. "Their business model has created a billion-dollar market. How do you make a billion-dollar market out of LED light devices?"